United Nations human rights chief Navi Pillay is voicing “deep disappointment” that the U.S. government has failed to close its detention facility at Guantanamo Bay (Cuba), as President Barack Obama pledged on taking office three years ago.

Pillay, in a statement Monday, noted the 10th anniversary of the prison opening and the third anniversary of Mr. Obama's inauguration promise to close the facility within 12 months. She also said that prisoners remain “arbitrarily detained indefinitely,” and called the detentions “a clear breach of international law.”

Pillay said she also remains “disturbed” by the government's failure to allow independent human rights monitoring of detention conditions at the facility.

Former President George W. Bush set up the prison at the U.S. naval base in Cuba, after U.S.-led forces went to war in Afghanistan against al-Qaida militant group behind the September 11, 2001 terrorist attacks on the United States.

Supporters say the facility is vital to the war effort, while critics say harsh interrogation procedures and several reported inmate suicides have damaged U.S. prestige abroad.

President Obama signed an order on January 22, 2009 temporarily suspending military court proceedings at the base and promising its closure. But in May of that year, the U.S. Senate blocked funds needed for the transfer of prisoners from the facility. U.S. officials have since said prospects for closing the prison are small, given broad opposition in the U.S. Congress to such a move.

Eight prisoners are known to have died there, most of them by suicide,